Magnetic sensor and torque sensing device having the same

Abstract

A sensor housing has a receiving recess at one end portion of the sensor housing located at one end of the sensor housing. The one end portion of the sensor housing faces first and second magnetic circuit portions. A circuit board is received in the receiving recess and has an opening, a front-side region and a rear-side region. The front-side region is located on a side of the opening where the one end of the sensor housing is placed. The rear-side region is located on an opposite side of the opening. A main body of a magnetic sensing device overlaps the opening such that terminals projecting from one of a pair of side walls of the main body are located at the front-side region, and terminals projecting from another one of the pair of side walls is located at the rear-side region.

What is claimed is: 
     
       1. A magnetic sensor configured to output an electrical signal corresponding to a magnetic flux generated between a first magnetic circuit portion and a second magnetic circuit portion which are opposed to each other, the magnetic sensor comprising:
 a sensor housing that has a receiving recess at one end portion of the sensor housing located at one end of the sensor housing, wherein the one end portion of the sensor housing is configured to face the first magnetic circuit portion and the second magnetic circuit portion; 
 a circuit board that is received in the receiving recess; 
 a magnetic sensing device that is installed to the circuit board and is configured to output the electrical signal which corresponds to the magnetic flux; and 
 a pair of magnetic flux guide members that are respectively made of a soft magnetic material and are configured to guide the magnetic flux to the magnetic sensing device, wherein the pair of magnetic flux guide members are opposed to each other while the magnetic sensing device is interposed between the pair of magnetic flux guide members, wherein: 
 the circuit board has:
 an opening; 
 a front-side region which is located on a side of the opening where the one end of the sensor housing is placed; and 
 a rear-side region which is located on an opposite side of the opening that is opposite to the front-side region; 
 
 the magnetic sensing device has:
 a main body which has a pair of side walls that are opposed to each other; and 
 a plurality of terminals which project outward from the pair of side walls such that one or more of the plurality of terminals project outward from one of the pair of side walls, and another one or more of the plurality of terminals project outward from another one of the pair of side walls; 
 
 the magnetic sensing device is installed to the circuit board such that the main body overlaps the opening in a normal direction that is perpendicular to a plane of the circuit board, wherein the one or more of the plurality of terminals projecting outward from the one of the pair of side walls is located at the front-side region, and the another one or more of the plurality of terminals projecting outward from the another one of the pair of side walls is located at the rear-side region; 
 one of the pair of magnetic flux guide members is placed in the opening; 
 the circuit board has:
 a first section which is placed away from the one end of the sensor housing; and 
 a second section, which is placed on a side of the first section where the one end of the sensor housing is placed; 
 
 the opening is formed in the second section to form the front-side region and the rear-side region in the second section; and 
 a direction, in which the first section and the second section are aligned, is defined as an alignment direction, and a width of the second section, which is measured in a direction intersecting the alignment direction, is smaller than a width of the first section, which is measured in the direction perpendicular to the alignment direction. 
 
     
     
       2. The magnetic sensor according to  claim 1 , wherein
 a cap which is formed separately from the sensor housing, is installed to the one end portion of the sensor housing. 
 
     
     
       3. The magnetic sensor according to  claim 2 , wherein
 an O-ring, which is a sealing material, is installed in a groove that is formed at an outer wall surface of the cap. 
 
     
     
       4. The magnetic sensor according to  claim 1 , wherein
 a waterproof covering material, which integrally covers the pair of magnetic flux guide members, the circuit board and the magnetic sensing device, is arranged in the receiving recess of the sensor housing. 
 
     
     
       5. A torque sensing device configured to output an electrical signal that corresponds to a torsional torque generated at a torsion bar in response to relative rotation about a rotational axis between a first shaft and a second shaft which are coaxially coupled through the torsion bar along the rotational axis, the torque sensing device comprising:
 the magnetic sensor of  claim 1 ; 
 the first magnetic circuit portion that is placed at one side of a multipole magnet in an axial direction of the rotational axis, wherein the multipole magnet has a plurality of magnetic poles which are arranged in a circumferential direction about the rotational axis such that polarities of the plurality of magnetic poles are alternately changed in the circumferential direction, and the multipole magnet is placed coaxially with the torsion bar such that the multipole magnet is rotated about the rotational axis in response to the relative rotation; and 
 the second magnetic circuit portion that is placed at another side of the multipole magnet in the axial direction, wherein: 
 the magnetic sensor is placed such that the pair of magnetic flux guide members are magnetically coupled to a magnetic circuit that is formed by the first magnetic circuit portion and the second magnetic circuit portion; 
 the pair of magnetic flux guide members include a first magnetic flux guide member, which has a main body opposed to the first magnetic circuit portion, and a second magnetic flux guide member, which has a main body opposed to the second magnetic circuit portion; and 
 each of the main body of the first magnetic flux guide member and the main body of the second magnetic flux guide member is configured as follows: 
 the main body has a pair of outer end portions that are respectively placed on one circumferential side and another circumferential side of a reference line which is an imaginary line being perpendicular to the rotational axis and intersecting the main body;
 a distance measured between the rotational axis and the main body is set such that the distance measured at each of the pair of outer end portions is longer than the distance measured at an intermediate portion of the main body circumferentially located between the pair of outer end portions; and 
 one or more of the plurality of magnetic poles of the multipole magnet is placed in a magnetic flux radiation range of the first shaft that is a circumferential range defined between two imaginary lines while a number of the one or more of the plurality of magnetic poles of the multipole magnet is within a predetermined range, wherein one of the two imaginary lines radially connects a radially inner side part of one of the pair of outer end portions to the rotational axis, and another one of the two imaginary lines radially connects a radially inner side part of another one of the pair of outer end portions to the rotational axis. 
 
 
     
     
       6. The torque sensing device according to  claim 5 , wherein
 each of the main body of the first magnetic flux guide member and the main body of the second magnetic flux guide member is configured such that the number of the one or more of the plurality of multipole magnet included in the magnetic flux radiation range is in a range of 1.2 to 2.8.